An automatic analyzer performs qualitative/quantitative analysis by adding a reagent specifically reacting to a specific ingredient contained in a living body specimen (hereinafter, referred to as a specimen) such as blood or urine, by causing the reagent to react therewith, and by measuring optical density or an emitted light quantity of reaction liquid.
According to this automatic analyzer, in order to cause the specimen and the reagent to react with each other, it is necessary to provide a step of dispensing the specimen which is an analysis target contained in a specimen container or the reagent which is added to and reacted with the specimen, into a reaction container. A small amount of the specimen or the reagent is dispensed into the reaction container. Accordingly, accurate dispensing inevitably affects accurate analysis.
Therefore, it is important to reliably detect abnormal dispensing which may lead to inaccurate dispensing.
In a step of dispensing the specimen into the reaction container, factors frequently leading to abnormal dispensing include probe clogging in a probe which is caused by aspirating solid substances such as fibrin. If clogging occurs in the probe, a predetermined amount of specimen cannot be dispensed into the reaction container, and thus it is not possible to obtain reliable analysis results. In addition, in a case where air bubbles or liquid films are present on a liquid level of a test specimen, the air bubbles or the liquid films are determined as the liquid level. Consequently, an originally planned amount of the specimen cannot be aspirated, thereby causing the abnormal dispensing. In order to avoid the abnormal dispensing in a case where the air bubbles or the liquid films are present, it is conceivable to increase the amount of the probe dipped into the test specimen. However, if the amount of the probe dipped into the test specimen increases, there is a possibility of increasing contamination and adversely affected analysis results.
Therefore, in order to minimize a depth of the probe dipped into the liquid as much as possible, an operation control method is generally employed in which the liquid level of the liquid inside the container is detected, a lowering operation of the probe is stopped at a position where a tip of the probe reaches slightly below the liquid level, and then, a predetermined amount of liquid is aspirated into the probe.
As means for detecting the liquid level of the test specimen, the most generally used one is an electrostatic capacity variation method of detecting variations in electrostatic capacity when the probe comes into contact with the liquid level.
However, as described above, in a case where a liquid level sensor is used in this way, if the air bubbles or the liquid films are present on the liquid level, these may be erroneously detected as the liquid level, thereby causing the abnormal dispensing.
In a step of dispensing the reagent into the reaction container, the abnormal dispensing is also caused to occur by aspirating the air bubbles generated on the liquid level of the reagent. If the amount of the probe dipped into the reagent increases similarly to a case of the specimen, there is a possibility of increasing contamination and adversely affected analysis results. Therefore, similarly to the case of the specimen, a probe operation control method is generally employed.
For example, as a technique of detecting the abnormal dispensing, PTL 1 discloses an automatic analyzer including at least one pressure sensor that detects pressure inside a dispensing channel connecting a probe which aspirates and discharges a sample and a dispensing syringe which generates the pressure for causing the probe to aspirate and discharge the sample, pressure value storage means for storing time-series output values of the pressure sensor during a sample dispensing operation, and storage means for storing a reference database having the time-series output values of the pressure sensor when the probe normally aspirates or discharges the sample.
Then, the automatic analyzer disclosed in PTL 1 above calculates the Mahalanobis distance from comparison data and the reference database which are prepared based on the time-series pressure sensor output values stored in the pressure value storage means, and determines the abnormal dispensing of the sample by comparing the calculation result with a predetermined threshold value.